July 2017

An interdisciplinary take on diabetic limb salvage

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Developing a multidisciplinary team dedicated to diabetic limb salvage allows for immediate referral, lessens the burdens on individual practitioners, helps remove structural barriers that can delay patient care, and offers a framework in which to organize inpatient care for these patients.

By Brian M. Schmidt, DPM, AACFAS

One of the most challenging aspects of practicing podiatric medicine in the 21st century is the difficulty a practitioner faces in obtaining expedited and immediate referrals to specialist providers whose care our patients require. Often, when a podiatric surgeon encounters a diabetic foot ulcer complicated by infection and a threat of tissue loss, he or she must act without delay.

One option is to send the patient to the emergency room for further evaluation. However, if the institution does not have a multi­disciplinary team to salvage the limb, the patient may be unnecessarily exposed to long-term parenteral antibiotics or a more aggressive major lower extremity amputation than is warranted. This not only increases costs unnecessarily, it can also increase patient mortality.1 Five-year mortality rates are higher in patients with diabetes-related or nontraumatic lower extremity amputations than in those affected with breast or prostate cancer.2 And, in the shorter term, 30-day mortality rates of 6.3% and 13.3% have been reported following below-knee and above-knee amputations, respectively.3

Podiatric physicians are trained to recognize infection, vascular insufficiency, venous disease, peripheral neuropathy, and poor patient compliance with medication regimens for diabetes or other medical comorbidities. Because of this, we are often the initial contact when a patient encounters a dire situation. And, because time is tissue when it comes to limb salvage, the podiatrist must have an excellent referral base. However, this can be difficult for clinicians who work in a private practice setting and may not have immediate access to many specialist providers. Complicating this further is the availability of those specialists to quickly see a patient who is facing limb loss.

Multidisciplinary approach

Successful referrals are best achieved when an individual provider can admit a patient to a large hospital. However, though many hospital systems have dedicated collaborative limb salvage teams—Georgetown University Hospital in Washington, DC; Southern Arizona Limb Salvage Alliance at the University of Arizona in Tucson; and Yale New Haven Hospital in Connecticut, to name a few—not every hospital system has such a team. The larger question that looms is how does one begin to form the institutional relationships necessary for development of a limb salvage interdisciplinary team?

Without multidisciplinary limb salvage, a patient may be unnecessarily exposed to long-term parenteral antibiotics or a more aggressive amputation than is warranted.

The multidisciplinary team consists of many physicians and allied health professionals who are aligned to facilitate the rapid referral and communication needed for optimal patient outcomes. The team typically includes podiatrists, endocrinologists, vascular and plastic surgeons, rheumatologists, orthopedists, and general medicine practitioners, who may also focus on infectious disease as a subspecialty. Other important team members include emergency physicians who can appropriately triage individual patients identified as high-risk for limb loss and immediately get them into the hands of the multispecialty team. Secondary team members include wound care specialists, along with residents and students. Each team member is important, and it is the intergroup communications and action that lead to improved outcomes.

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An important parameter for ensuring appropriate referral to the limb salvage service is the use of algorithms and guidelines for referrals. This can be as simple as using and documenting a diabetic foot risk score4 and implementing it in all services through education and information dissemination. Stratifying based on high-, medium-, or low-risk score5 systems allows all clinicians involved in the care of a patient with diabetes to have some common understanding of the severity of any comorbidities. With the advent of electronic medical records, risk stratification also gives the practitioner tools with which to study and analyze outcomes in patients who present to the limb salvage team.

Alternatively, a dedicated inpatient service can be formed for rapid identification of at-risk diabetic limbs. My institution (the University of Michigan Medical School in Ann Arbor) has implemented algorithms to identify not only diabetic foot infections and ulcerations, but to immediately obtain noninvasive vascular studies while consulting podiatry and vascular services so the patient is placed into the correct hands immediately. Anecdotally, this has already led to more partial foot amputations and fewer major lower extremity amputations. In either case, communication among the group members, as well as between the group and the patient, is critical. If every team member is knowledgeable about one another’s expertise and experience, it is more likely that appropriate referrals will happen. This is the first step in the creation of a limb salvage program.

Getting started

Starting from nothing, without a dedicated limb salvage service, establishing an inpatient service or a goal-oriented interdisciplinary team can be difficult and will take time. To start the process, one should be well versed in the literature surrounding most current limb salvage efforts and identify individuals from all specialties who have an interest in limb salvage. This can be done both in the community and at the institutional level. Second, one should prepare to educate staff and colleagues about the benefits of limb salvage and how each team member, including the podiatrist, is an integral part of this process. Limb salvage includes not only preventing major lower extremity amputations, but also can involve vascular reconstructions along with pedal reconstructions to obtain a functional limb.6-9 These efforts may excite members of other disciplines with opportunities to advance limb salvage.

Individuals also can become active members in local, regional, and national organizations that collaborate on the topics related to diabetic foot care and limb salvage. Podiatrists can actively become physician members of the Society of Vascular Surgeons, for example, which could improve one’s standing with community physicians in establishing a multidisciplinary diabetic foot service. This type of membership also will provide podiatrists with educational opportunities to better realize what physicians from different specialties can add to the limb salvage team. Finally, research opportunities are boundless when working with multiple specialties, and this type of collaboration can add synergy to outcome-based assessments. These educational endeavors will initiate the process for developing a limb salvage team.

Limb salvage literature

The benefits of limb salvage speak for themselves, and increasingly are being documented in the medical literature.

In a study from Tacoma, WA, at the Madigan Army Medical Center, the initiation of a Limb Preservation Service dedicated to collaborative medicine resulted in an 82% decrease in lower extremity amputations over five years.10 The rate of lower extremity amputations was reduced from 9.9 per 1000 patients to 1.1 per 1000 patients. This accounted for an absolute reduction of 24 major lower extremity amputations in four years. Even more impressive was that this center, during the same period, saw a 48% increase in the volume of diabetes cases.10

A study in 2015 from the Center for Limb Preservation at the University of California, San Francisco reported similar results.11 This group demonstrated that the majority of neuroischemic wounds treated by a multidisciplinary team healed within 12 weeks. Secondarily, they had only three major amputations in a group of 91 limbs plus an effective major-to-minor amputation ratio of .06. For comparison, the most recent major-to-minor amputation ratio at my institution was .60.12 However, the study cautioned that rearfoot and midfoot wounds can recur and in particular, hindfoot ulcers were predictive of failure to heal, with an odds ratio of .21;11 this makes the aforementioned risk scores and surveillance vital.

Conversely, research suggests that partial foot amputations are associated with decreased mortality compared with higher-level amputations.13 Looking specifically at transmetatarsal amputations (TMA), healing rates above 65% are achieved when revascularization is combined with TMA.14 However, end-stage renal disease does increase the morbidity associated with this amputee cohort.14

More concerning are rehabilitation statistics surrounding higher-level amputations. With respect to higher-level amputations, only 5% of lower-limb amputees use their prosthesis for more than half of their waking hours,15 and the proportion of total wheelchair users in this group rises from 13% in the first year after surgery to 39% after five years.15

TMA trials

A recent study16 looked at nursing home residents who underwent below-knee (n = 1596), above-knee (n = 2879), or transmetatarsal (n = 490) amputation. In this population—more than 70% which had diabetes—patients who had transmetatarsal amputations returned to baseline function by six months postoperatively, but those who had higher-level amputations did not.16

It has also been shown that the 30-day postoperative mortality of a transmetatarsal amputation is 3%,17 which compares favorably to the 30-day mortality rates of 6.3% and 13.3% associated with below-knee and above-knee amputations,3 respectively, as mentioned earlier. More recent data suggest TMA mortality rates based on survival analysis at one, three, and five years were 0%, 5%, and 3%, respectively, and are lower than those associated with higher-level amputations.2,18 In comparison, a separate study reported 30-day postoperative mortality of 6.3% for below-knee amputation and 13.3% for above-knee amputation (63% of the below-knee amputees and 38.7% of the above-knee amputees had diabetes).19

Although these comparisons pertain only to minor amputation at the transmetatarsal level, they suggest limb salvage can help patients achieve better outcomes, including functional ability and survival; utilizing all resources available to the physician can help ensure appropriate amputation levels for all patients and, in turn, can help optimize post-amputation outcomes.

A new hypothesis about differences in mortality among patients with diabetes who receive partial foot amputations and transtibial amputation suggests patients undergoing more proximal amputations have more comorbidities,20 but this thought is chronologically myopic. Among patients with diabetes, five-year mortality does not differ significantly between those with and without nontraumatic partial foot amputations; after 10 years, however, a difference is realized.13 In due time, comorbidities do “catch up” to patients, but minor amputations extend that interval compared with higher-level amputations.

Our experience

At my institution, an interdisciplinary approach was implemented shortly after it established a podiatry service in 2006, in collaboration with the endocrine division, to aid in diabetic foot care and reduce related complications.

The simple addition of podiatry services led to an approximately tripling of the rate of limb salvage, as measured by the change in the high-low amputation ratio over a 10-year period (the ratio is defined by the number of above- and below-knee nontraumatic amputations divided by the number of minor nontraumatic amputations).12

The addition of podiatry services also led to approximately 40 limbs being salvaged per year on average compared with the era without podiatry services. This finding was statistically significant,12 validates previous and current work in limb preservation, and supports adding podiatrists to the limb salvage team at any institution.

Conclusion

A multidisciplinary team dedicated to limb salvage has many benefits, so it is unfortunate that too few patients with diabetes have access to this type of collaborative treatment. Services dedicated to limb salvage are not widespread outside the academic world, and there is ample opportunity at many hospitals and medical centers to establish a team.

The benefits are multifactorial. First, and most important, patients have access to the newest techniques from different specialties to salvage as much of the limb as possible. The literature clearly suggests there is often a decrease in the rate of major lower extremity amputations and an increase preservation of functional limbs when these teams are established. Second, the team approach encourages all members to gain greater understanding of the different body systems that can contribute to lower extremity pathology; this includes making a specialist’s esoteric knowledge accessible to all team members. Anecdotally, this improves institutional logistics and patient care. Third, access to a limb salvage center enhances research opportunities for all clinicians involved. This can include the analysis of slight nuances that confound patient outcomes in this cohort, which can further improve patient outcomes. Finally, a limb salvage team disseminates information to the patient and allows for more focused and regular care.

Patients are more closely monitored because of the formation of an outpatient clinic involving various specialties. The outpatient setting coordinates care and continues the care given as an inpatient. The outpatient clinic also makes close follow-up with patients more manageable. The limited time commitment by one physician is protected by the general interest of all participating groups.

One of the most challenging aspects of practicing podiatric medicine in the 21st century is the difficulty a practitioner can face in obtaining expedited and immediate referrals to specialist providers whose care our patients require. The most difficult barrier to overcome in developing a program is inaction. The development of a multidisciplinary team dedicated to limb salvage allows for immediate referral and lessens the burdens on individual practitioners. It helps remove structural barriers that can delay patient care. And it offers a framework in which to organize care for these patients once they have reached the inpatient setting.

Brian M. Schmidt, DPM, AACFAS, is a clinical assistant professor in the Department of Internal Medicine, Division of Metabolism, Endocrinology, and Diabetes, at the University of Michigan Medical School in Ann Arbor.

REFERENCES
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